Excavation collapse with two fatalities

[dgillette]

Don't know any details beyond what's in the article.

http://www.google.com/hostednews/ap/article/ALeqM5ib2grNCUQNwaTTsZMzgrG46xUamwD9DTL2F81

 

[msucog]

saw a snipit of it on the news...looked like a very deep hole to be in. been in deep excavation that caved before myself in my younger/naive days...word of advice: dont be stupid...be safe. i was lucky and am now a bit wiser because of it.

Ryan Coggins, P.E., S.I.

http://www.linkedin.com/in/ryancoggins

 

[Mccoy]

Are there any specific regulations or procedures about trench and excavations stability with workers into them?

Here in Italy, for example, it is forbidden to leave the faces unsupported when the height is greater than 1.5 meters (5 feet).
The employer ignores that, a worker gets buried and dies after a collapse, the employer is a dead horse.

Unless there is a geologist's (or engineer's) report stating that the face can be considered stable even if unsupported for a larger height.

It is all too obvious how tricky it may be to sign such a report, unless a very detailed site investigation is carried out, also allowing for the linear development of some earth works like trenches.

it is also too easy to understand how many employers are tempted to ignore the regulations and take a risk.

 

[dgillette]

http://www.osha.gov/pls/oshaweb/searchresults.relevance?p_text=excavation

Hi McCoy. As this link will show you, we have extensive, detailed regulations in the US. Sometimes, they seem unnecessarily strict, but that's not all bad.

My next door neighbor is on permanent disability as a result of a trench caving in on him while he was building a pipeline. When I had work done on my house recently, he lectured me up, down, and sideways about making sure the exc slopes were adequate. (I don't think he actually knew what I do for a living.)

Best regards,
DRG

 

[Mccoy]

Thanks for the reference, dgillette, I found particularly interesting the following:

Each employee in an excavation shall be protected from cave-ins by an adequate protective system designed in accordance with paragraph (b) or (c) of this section except when:
1926.652(a)(1)(i)
Excavations are made entirely in stable rock; or
1926.652(a)(1)(ii)
Excavations are less than 5 feet (1.52 m) in depth and examination of the ground by a competent person provides no indication of a potential cave-in.
1926.652(a)(2)

Of course there must be some competent person to ensure that the 'stable rock' is actually stable.
I construe the word 'rock' as in lithified rock, which rules out soil, loose or cemented unless cement is very hard.

It's interesting the double constraint imposed on loose soil.

Height < 5 feet AND no indications of potential cave-ins.

Which makes up a more rigorous constraint than the one in the Italian regulations (only the height constraint is present).

Some other things are similar, on the whole the OSHA regulations appear to be a little more detailed than the Italian ones.

 

[structuresguy]

I used to be a construction inspector for a natural gas utility, supervising contractor work crews installing gas pipelines, both distribution and service lines. For us, any hole more than 4 feet deep had to be shored, or sloped at a 2 horz to 1 vertical slope maximum. We were very strick with the contractor about it too.

One time, myself and the chief inspector (who was also the chief safety official for the utility) arrived at a site where the crew was running a new gas line up a road in the city. The trench was about 3 feet wide and about 4.5 feet deep, with about 8 inches of asphalt at the top layer (cut through the road). When we arrived we noticed the depth of the trench and were telling the crew foreman that it needed shoring. He was arguing with us that since it had asphalt on top, the dirt was not over 4 feet.

Well, literally as he was arguing, the sides caved in at one location, and trapped a worker. He fell onto his knees when the dirt hit him, and was buried up to just below rib cage or so. Fortunatly, he was still upright, so head and shoulders were up above the dirt. It took several guys several minutes to dig him out from that. If he had been knocked down flat on the bottom of the trench, he likely would have suffocated. And that is just with only 4 feet of dirt. Needless to say, several people got in big trouble over that incident, including the gas company inspector who was on-site before we arrived.

Just wanted to point out that even seemingly shallow excavations can be very dangerous. Please take care if you are ever in that sort of scenario. Remember, dirt weighs 100+ lbs per cubic foot. So with even only 2 feet of dirt on you, that is over 200 psf of pressure on every part of your body. Imagine having 200lb person stand on your chest. Now try breathing. And that only works out to about 100psf, based on the area of the footprint of the person. No weigh could the average person have 3feet or more of dirt on them, and still be able to breath, much less dig their way out.

 

[Mccoy]

He was arguing with us that since it had asphalt on top, the dirt was not over 4 feet. Well, literally as he was arguing, the sides caved in at one location, and trapped a worker.

Impressing timing for the trench to cave-in

I witnessed a few trench cave-ins, when digging with no workers inside and the scenery is sure pretty disturbing.

I believe I've already reported in these boards about a professor in my place who was studying superficial alluvial deposits by digging trenches. He was smart in that he never went down the trenches, he let other geologists get down into the bucket of the excavator.

One time the excavation outsmarted him though. While he was observing from the edge of the trench, a cave-in occurred and he happened to be just on the surface of the unstable wedge, which ruined down.

When his body was unburied he was long dead.

 

[theCorkster]

It's possible to die in a cave in even though you are standing erect with direct contact with air. Every time you exhale and your lungs contract, the soil will tend to move into the space, further constricting your ability to re-expand your lungs and take your next breath.